The invention relates to a display unit comprising an optical waveguide.
Display units of this type are used in technical devices, for example radio receivers (DE-PS No. 905 488, DE-PS No. 944 739, DE-AS No. 23 27 924), motor car control or operating members (DE-AS No. 21 44 588, DE-OS No. 29 37 041, DE-OS No. 37 04 574), clocks (DE-OS No. 33 13 463) and electric household appliances such as electric cookers, washing machines and dish washers (DE-OS No. 36 03 324), the optical waveguides usually being made of a synthetic resin material. The optical waveguide may optionally conduct coloured light (DE-PS No. 944 739) or it is made of a light-collecting and light-conducting material, preferably containing a fluorescent dye (DE-PS No. 36 03 324).
Fluorescent dyes having light-collecting and light-converting properties are disclosed in inter alia the DE-OS No. 28 51 513, 30 01 857, 30 16 765 and 32 35 526 and the EP-PS No. 81 766 (perylene derivatives), the DE-PS No. 25 136 and 32 670 (cumarin derivatives) and the EP-OS No. 32 373, 46 861 and 73 007 (further organic compounds). In the DE-OS No. 28 51 513 and in the DE-PS No. 81 766 reference is made to the DE-AS No. 24 51 781 and/or 24 51 782, according to which the perylene derivatives are suitable for dying polystyrene, polyacrylate or polycarbonate in the mass, wherein for example 0.1 part of the dye is mixed with 100 parts of milled polystyrolblock polymerisate and 1 part of titanium dioxide. Subsequently the mixture is subjected to a further treatment, for example in a mixed salt unit or in a melting furnace.